by Merijn Pen | Jul 10, 2017
Florian Niekiel, M.Sc.
Lehrstuhl für Mikro- und Nanostrukturforschung & Center for Nanoanalysis and Electron Microscopy (CENEM), Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany Authors | Florian Niekiel, Peter Schweizer, Simon M. Kraschewski, Benjamin Butz and Erdmann Spiecker Email | Erdmann.Spiecker@ww.uni-erlangen.de
| Application |
The Process of Solid-State Dewetting of Au Thin Films Studied by In-situ Scanning Transmission Electron Microscopy |
| Authors |
Florian Niekiel, Peter Schweizer, Simon M. Kraschewski, Benjamin Butz and Erdmann Spiecker |
| Journal |
Acta Materialia, 2015 |
| Keywords |
Solid-state dewetting; Thin films; Morphology; Temporal evolution; Image analysis |
| Publication / D.O.I. |
Full Publication Here |
The Process of Solid-State Dewetting of Au Thin Films Studied by In-situ Scanning Transmission Electron Microscopy
ABSTRACT: Solid-state dewetting describes the transformation of thin films into a set of particles or droplets at temperatures well below the melting temperature of the bulk. In this work in situ scanning transmission electron microscopy has been used to study the dewetting behavior of discontinuous Au thin films (15 nm and 22 nm thick) on amorphous silicon nitride membranes at temperatures ranging from 300°C to 600°C. The combination of microscopic and statistical information enabled not only the qualitative discussion of the observed processes but also the quantification of the kinetics as well as the development of a model of the underlying morphological mechanism. A model-free master curve approach to the temporal evolution of the covered area at different temperatures is used to determine the activation energy of dewetting (1.04 ± 0.14 eV for the 15 nm thick film). A closer inspection reveals a multiple power law behavior, which is discussed in the frame of depercolation. Retraction of finger-like structures is found to be the dominant morphological mechanism based on the observed linear relationship between covered area and boundary length.
FIGURE RIGHT: 15 nm (left) and 22 nm (right) thick Au films in the as-deposited state: (a) plan view HAADF-STEM images, (b) cross sectional TEM bright field images of respective lift-out lamellae.
FIGURE BELOW: Comparison of HAADF images from the in situ STEM experiments on the 15 nm thick Au films. Experiment time t is indicated by red labels.
FIGURE BELOW: Comparison of HAADF images from the in situ STEM experiments on the 22 nm thick Au films. Experiment time t is indicated by red labels.
by Merijn Pen | Jul 10, 2017
Drs. Li Yueliang
National Center for Electron Microscopy in Beijing, Tsinghua University, Beijing, China Authors | Yueliang Li, Zhenyu Lia, Fang Fang, Xiaohui Wang, Longtu Li and Jing Zhu Email | jzhu@mail.tsinghua.edu.cn
| Application |
Significant Increase of Curie Temperature in Nano-scale BaTiO3 |
| Authors |
Yueliang Li, Zhenyu Lia, Fang Fang, Xiaohui Wang, Longtu Li and Jing Zhu |
| Journal |
Applied Physics Letters, 2014 |
| Sample |
Particles |
| Topic |
Phase Mapping, Thermal Stability, Size-property Relation |
| Field |
Chemistry, Material Science, Electronics |
| Techniques |
HREM |
| Publication / D.O.I. |
Full Publication Here |
Significant Increase of Curie Temperature in Nano-scale BaTiO3
ABSTRACT: The low Curie temperature (Tc = 130 °C) of bulk BaTiO3 greatly limits its applications. In this work, the phase structures of BaTiO3 nanoparticles with sizes ranging from 2.5 nm to 10 nm were studied at various temperatures by using aberration-corrected transmission electron microscopy (TEM) equipped with an in-situ heating holder. The results implied that each BaTiO3 nanoparticle was composed of different phases, and the ferroelectric ones were observed in the shells due to the complicated surface structure. The ferroelectric phases in BaTiO3 nanoparticles remained at 600 °C, suggesting a significant increase of Tc . Based on the in-situ TEM results and the data reported by others, temperature-size phase diagrams for BaTiO3 particles and ceramics were proposed, showing that the phase transition became diffused and the Tc obviously increased with decreasing size. The present work sheds light on the design and fabrication of advanced devices for high temperature applications.
Figure left: (a)–(c) Atomic resolved TEM images of BaTiO3 nanoparticles with the incident electron beam parallel to (100), (110), and (111), recorded at 200 °C, 25 °C, and 400 °C, respectively. (d)–(f). The distribution mappings of possible phases related with the corresponding symmetry, where phase with high symmetry locates in cool areas and low symmetric phases locate in warm areas.
Figure left: Phase distribution maps of six different particles with the similar size (4-5 nm) at (a) 25 C, (b) 100 C, (c) 200 C, (d) 300 C, (e) 400 C, and (f) 600 C, respectively. All the particles are composed of various phases including ferroelectric phases with lower symmetry, implying that ferroelectric phases could remain at 600 C and the Tc increases to at least 600 C in BaTiO3 nanoparticle.
DENSsolutions Comments:
Developing better technologies for efficient use of our nature resource relies on advances in new and improved nanostructure and nanomaterials. Understanding size-property relation play a crucial role in designing functional devices. (S)TEM, with enhanced by recent aberration correction, has become a powerful tool for nanomaterials characterization. It has the unique ability to image the size, shape, bulk/surface/interface structures of individual nano objects at sub-angstrom scale. Characterization of the particles over the whole temperature range provides a direct measurement of the thermal stability of the nano-objects. The link between the size and the thermal property of the particles is then able to be obtained.
The DENSsolutions heating system provides the minimal specimen drift at elevated temperature. The atomic structure of the sample, even light atoms, e.g. Oxygen, can be clearly imaged with high precision at elevated temperature, allowing different domain structures determined within nm size particles.
by Merijn Pen | Jul 10, 2017
Drs. Anil O. Yalcin
Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
Authors | Anil O. Yalcin, Bart Goris, Relinde J. A. van Dijk-Moes, Zhaochuan Fan, Ahmet K. Erdamar, Frans D. Tichelaar, Thijs J. H. Vlugt, Gustaaf Van Tendeloo, Sara Bals, Daniël Vanmaekelbergh, Henny W. Zandbergen and Marijn A. van Huis. Email | A.O.Yalcin@tudelft.nl
| Application |
Heat-induced Transformation of CdSe–CdS–ZnS Core–multishell Quantum Dots by Zn Diffusion into Inner Layers |
| Authors |
Anil O. Yalcin, Bart Goris, Relinde J. A. van Dijk-Moes, Zhaochuan Fan, Ahmet K. Erdamar, Frans D. Tichelaar, Thijs J. H. Vlugt, Gustaaf Van Tendeloo, Sara Bals, Daniël Vanmaekelbergh, Henny W. Zandbergen and Marijn A. van Huis. |
| Journal |
Chem. Commun., 2015,51, 3320-3323 |
| Publication |
Full Publication Here – DOI: 10.1039/C4CC08647C |
Heat-induced Transformation of CdSe–CdS–ZnS Core–multishell Quantum Dots by Zn Diffusion into Inner Layers
ABSTRACT: In this work, we investigate the thermal evolution of CdSe–CdS–ZnS core–multishell quantum dots (QDs) in situ using transmission electron microscopy (TEM). Starting at a temperature of approximately 250 °C, Zn diffusion into inner layers takes place together with simultaneous evaporation of particularly Cd and S. As a result of this transformation, CdxZn1−xSe–CdyZn1−yS core–shell QDs are obtained.
Figure Right: (a) HAADF-STEM image of CdSe–CdS–ZnS core–multishell QDs at their initial state at RT. (b–f) The corresponding Se, S, Cd and Zn elemental maps and an overlay of the Cd and Zn elemental maps obtained by EDX mapping. The scale bar in (a) applies also to (b–f). (g and h) HRTEM images of two QDs along two different zone axes.
Figure below: (a) HAADF-STEM image of QDs at 275 1C. (b–f) The corresponding Se, S, Cd and Zn elemental maps and an overlay of the Cd and Zn elemental maps obtained by EDX mapping. Elemental maps indicate that CdSe–CdS–ZnS QDs transformed into CdxZn1xSe–CdyZn1yS core–shell structures by Zn diffusion into the inner layers. The scale bar in (a) applies also to (b–f).
Figure below: High resolution HAADF-STEM study of a QD during thermal evolution at temperatures of (a) 120 1C, (b) 270 1C, and (c) 310 1C. The FT of each image is placed below the image. The scale bars in (a) and in thecorresponding FT apply to all images and FTs. .
by Merijn Pen | Jul 10, 2017
Dr. Jens Kling
Technical University of Denmark Authors | Jens Kling, Christian D. Damsgaard, Thomas W. Hansen & Jakob B. Wagner. Email | jenk@cen.dtu.dk
| Application |
Quantifying the Growth of Individual Graphene Layers by In Situ Environmental Transmission Electron Microscopy |
| Authors |
Jens Kling, Christian D. Damsgaard, Thomas W. Hansen & Jakob B. Wagner. |
| Sample |
Particles |
| Topic |
Catalysis, Chemical Reaction, Kinetics |
| Techniques |
ETEM, HREM |
| Publication Link |
http://dx.doi.org/10.1016/j.carbon.2015.11.056 |
Quantifying the Growth of Individual Graphene Layers by In Situ Environmental Transmission Electron Microscopy
ABSTRACT: The bottom-up approach where materials are built atom by atom are becoming more and more common to create next generation of electric and optical devices. For instance, heterostructured semiconductor nanowires, carbon nanotubes and graphene those with excellent electron mobility and band gap structure, are the examples of materials synthesized via a bottom up approach. The atom-by-atom building scheme is highly dependent on synthesis parameters such as temperature, precursors, and time of synthesis. The resulted structures finally determines the macroscopic properties, such as strength, brittleness, electric, magnetic, optical properties and catalytic performance, etc. In order to tailor materials for specific applications, control of the synthesis parameters for obtaining the desired materials structure is necessary.
Achieving in situ TEM observation of chemical synthesis process enables chemical reaction kinetics and mechanisms to be followed at the nanoscale, even at atomic scale. The insights provided by in situ TEM observations can be exploited to facilitate robust scaling of nanoscale synthesis processes to the manufacturing scale
Figure left: Growing layered carbon structures on a nickel catalyst using acetylene (C2H2) as precursor: Ni is firstly heated in situ in the ETEM to the growth temperature 650°C in the presence of hydrogen (H2). Switching C2H2 into the microscope at this temperature results in the formation of carbon layers on the Ni surfaces. Image series (a)-(d) with 0.61s time intervals indicate the in-plane growth of the carbon (see arrows). The images are acquired approximately 100s after introduction of C2H2. T= 650⁰C, P(C2H2)= 3×10-2Pa.
Video left: Images from in situ growth experiments performed at 600°C in C2H2. (a) and (b) shows two different characteristic areas after growth. The carbon layers appear less defined in most of the areas. T= 600⁰C, (C2H2)= 3×10-2Pa.
DENSsolutions Comments:
Understanding gas–solid interaction involved in materials synthesis and their functioning is central to the ability to control them. However, it has been clear that measurements performed on reactants and products are often not sufficient to determine the dynamic state of materials/samples ‘in operation’. Therefore, direct observations of chemical reactions down to atomic scale are of utmost importance.
DENSsolutions Heating System provides a unique platform for the detailed study of chemical synthesis/process at environmental TEM (ETEM). DENSsolutions has a fast feedback control system that stabilizes the sample immediately when changing parameters such as pressure and temperature, opening the possibility of HREM imaging of a transient event. Furthermore, the system provides accurate temperature readout at various gas environments (composition & pressure) and even during the change of the environment such that optimization of the growth parameters can be achieved in a reliable and efficient way
